# encoding: utf-8

import numpy as np
import math




#使用numpy导入数据

# print(t2)
# file_name = "E:/crp_linux1/build/bin/bin/Debug/pos/robotLineMotion.txt"
# data = np.loadtxt(file_name, delimiter=',')


# len = data[:,4]
# print(len)
# total = 0
# for i in range(len.shape[0]):
#     total = total + len[i] - 78

# total = total * 0.002

# print(total)

a = 3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280
b = 2.0 * a
print("%.20f" % b)